Process of making disintegratable top shot wads



Patented June 10, l$52 UNETE STATES PATENT FFEQE PROCESS OF MAKING DISINTEGRATABLE TOP SHOT WADS No Drawing. Application December 6, 1948, Serial No. 63,855

2 Claims. 1

This inventionrelates to a process of making disintegrating top shot wads of the type dis closed and claimed in the copending application of Harold 0. Russell Serial No. 609,238, filed August 6, 1945, and now abandoned.

The common shot shell cartridge made prior to said Russell application consisted of a shell component made of a rolled paper tube closed at one end by athin metal cup, usually of brass, which was shaped to provide the ejector flange and served 'to hold the central primer cap. In the common sequence of shotgun shell (shot shell), loading powder is first introduced into the tube-cup component and covered by a thick powder wad of hair felt or flexible cork comthe latter being held in place by a roll-crimp in the end of the paper tube.

Shot shells of this type are subject to the disadvantages because the top shot Wad in at least a certain percentage of the shells tends to impede the shot when fired and cause maldistribution of the shot pellets. The thick powder wad causes no trouble because it is below the shot load in the shell and trails behind the shot (known as the shot-string) when the shell is fired. For many years it was known that when fired, some shot shells produced what is known as a blown pattern wherein large areas within the usual pattern circle would receive few or no shot pellets. The faet that the top shot wad caused this unsatisfactory performance was not known and bad performance was accepted because, up to the time of said Russell invention of application Serial No. 609,238, better performance could not be obtained in any known shot shell construction havinga top shot wad. This was the reason for the development of the so-called wadless crimp shoe shells which give a satisfactory pattern at the expense of lesser loading space within the shell interior, and hence at the expense of fire power.

After extensive research both in the laboratory and in the field, including actual photographing of many shot charges as fired, the aforesaid Harold C. Russell discovered that the blown pattern phenomena was due to the fact that when the shell was fired the top shot wad remained intact or nearly so, and in a large percentage of shells, the top shot wad would be- 2 and the top shot wad thereby caused poor distribution of the pellets. This difilculty in shot shell performance was solved by the invention of the disintegrating top shot wads described and claimed in the aforesaid application Serial No. 609,238.

The present invention is a result of continued research on the subject and is directed to the problem of commercial production of disintegrating top shot wads for the aforesaid improved shot shells containing said disintegrating wads. It is an object of this invention to provide improved methods of manufacturing disintegrating top shot wads and particularly to provide methods of manufacture whereby wads of great uniformity in respect to the qualities of size, density and frangibility can be produced at costs which are entirely in keeping with commercial production costs.

It is also an object of the invention to provide methods of making top shot wads under controlled conditions.

It is a further object of the invention to provide methods of making disintegrating top shot wads of urea-formaldehyde resin impregnated paper board, particularly by a continuous process.

Other and further objects of the invention are those inherent in the methods herein described and claimed.

In carrying out the invention there is utilized an absorbent cellulosic fiber paper board stock, such as pulpboard stock in any desired thickness, preferably of a thickness ranging from about .030 inch to .060 inch. The absorbent paper board stock is first dipped into an aqueous syrup of urea-formaldehyde having a solids content of approximately 1.80 to 2.00 pounds of resin per gallon. The urea-formaldehyde resin stock may be obtained in the market but is preferably prepared fresh just prior to impregnating the paper board sheet. The saturated sheet of paper board is then partially dried with warm air so as to reduce the water content of the syrup impregnated board. The paper pulpboard should be contacted with the syrup for a sufiicient time period to allow substantially complete penetration of the syrup into the fibers of the board. During the preliminary or partial drying period the resin polymerizes only slightly and the impregnated and partially dried sheet is still flexible. The sheet is then treated with a solution of catalyst for the resin. This may be accomplished by passing the partially dried syrup-impregnated sheet through rollers saturated with a solution of catalyst. As the catalyst there may 3 be used a dilute solution of mineral acid such as dilute phosphoric, hydrochloric or the like catalyst, or a solution of an acid reacting salt, such as ammonium chloride, zinc chloride, or other acid reacting salts, such as alum. The exposure of the partially dried resin impregnated sheet to the catalyst greatly accelerates the polymerization of the resin and the impregnated board quickly hardens. The pulpboard is maintained straight and level during the final. stages of hardening and final drying.

The final polymerized, hardened and dried impregnated pulpboard is then. passed through a punch press which cuts small disks of suitable size to fit neatly into the interior of the shot shell tube being manufactured, The finished individual disks may be printed on usual presses for applying shot load designations.

The finished top shot wad disks are frangible, yet sufiiciently tough to stand up well in loading machines in which they may be handled with even greater ease than ordinary prior art. shot shell top wads, which had a tendency to stick together. The improved (disintegrating) top shot wads produced in accordance with the present invention do not hang together in the loading machine feed tubes and loading can be accomplishedwith greater ease than with prior art top shot wads. The topshot wad disks of. the present invention can be printed without breaking; they can be shipped and stored without deterioration; they are not subject to absorption of moisture, either prior to assembly or when assembled in the shell. What is most important, the. top shot wad disks are strong, yet can be broken by bending with the fingers. and when loaded as top shot wads and the shells fired, the top. shot wads disintegrate into countless tiny fragments smaller than the shot pellets and do not impede the. pellets.

We prefer to carryout the method of our invention by a continuous process wherein the absorbent sheet, such as pulpboard of appropriate thickness is unrolled from a supply roll and is passed'directly through. a dipping tank containi-ng the urea-ormaldehyde syrup. The thus dipped and urea-formaldehyde syrupv impregnated sheet is then pa-rtially dried with a current of hot air, preferably heated to 300-4'.0.0 B. After the water content is reduced nearly to dryness,

but whilev the impregnated sheet is still pliable, itis passed between. rollers saturated witha solutionof catalyst, preferably phosphoric acid having a concentration of less than.10% preferably 5%,.and then drawn througha final drying, pass Preparation of resin syrup 55.. gallons of 37% formaldehyde solution, or its equivalent. of weaker or stronger formaldehyde solution, wasrun into. a 150 gallon stainless steel still equipped with a reflux condenser. To

this there was added 9000 cc. of 28% ammonium hydroxide and then there was added 530 cc. of 10% sodium hydroxide solution. In place of the ammonium hydroxide, an equivalent of ammonia. (NI-I3). may be used- Finally there was added 175' pounds of powered urea. The urea was added slowly and dissolved in the liquid with stirring. The mixture was then heated with steam to C. by means of a stainless steel heating coil. The steam was turned ofi soon after the reaction began as the heat generated by the reaction was sufiicient to bring the temperature up. to. C. After the initial heat of reaction had diminished, the temperature was maintained at 95? C. for two hours by means of steam which was passed through the heating coil. The resin solution was then allowed to cool and was diluted by the addition of 27 gallons of resin to 21 gallons of water. The solution was used for impregnating the 'pulpboard sheet. When more concentrated or less concentrated solutions offormaldehyde, ammonium hydroxide and sodium hydroxide are used, correspondingly greater or lesser amounts of water are added upon dilution at the end of the syrup making process. The syrup should preferably contain from 1.80 to 2.00 pounds of resin (dry basis) per gallon of water, and when required the pH should be adjusted to the range of pH 6.8-8.2 by the addition of suitable amounts of sodium hydroxide.

Impregnatz'on of absorbent paper board stock The diluted resin solution was then placed in a tank equipped with rollers for guiding the strip of pulpboard paper stock therethrough and the temperature of the syrup impregnating, solution was held at '70-85 C. by means of a hot water jacket. During the. course of the impregnating run the syrup has a tendency to. become more acid, and the pH of the; syrup was therefore determined from time tov time and enough. 10% sodium hydroxide added as needed in order to maintain the pH of the syrup. treating solution between pH 6.8 and pH 8.2.

The absorbent paper used was a natural shade pulpboard .635 inch in thickness and 25 inches Wide and was received in 400 pound rolls, although pulpboard of greater or lesser thickness may be used. A dipping time of 4 to 5 minutes was required and during this time the paper traveled through the resin tank and became. thoroughly saturated with. the resin. During this period the paper remained immersed for approximately l l feet, during which time the paper remained in contact with the syrup. In some iii-- stances better impregnation can. be obtained by the addition of wetting agent, such as "MP 189 manufactured by E. I. du Pont de Nemours Co. or Nacanol. manufactured by National Aniline Co., which is added in an amount ranging from /2 to 1% of the. volume. of. the syrup. solution. The. penetration of the resin into the paper, however, canbe accomplished without the addition of. a wetting agent and was,- not used in this run.

Drying the resin soaked paper pulpboard' Approximately 17 to 18 minutes, was required to, dry the impregnated paper pulpboard. This was. accomplished by passing the syrup impreg nated paper pulpboard through. a current of. dry air heated to 300-400 F. During this drying period the paper was passedv continuously throughv the drying chamber over a number of rolls .orpasses. It. is preferable to maintain.- the.

drying chamber under slight vacuum by means of a blower so as to prevent the drying fumes from passing into the factory room where the drying is accomplished, and this was done in this run.

Polymerization and hardening of preliminarily and partially dried resin impregnated sheet The partially dried resin impregnated sheet, while still flexible, was run through two felt rollers saturated with a phosphoric acid solution in water containing phosphoric acid and partially dried syrup impregnated sheet after having acid applied thereto was passed through a second drier or section of the drier. The

addition of the acid, which was a catalyst for the resin, quickly hardened the syrup impregnated paper and during the finished drying the paper was maintained straight and level, at least during the final portion thereof when the impregnated paper was becoming stifi' and hard. It is sometimes feasible to make a pass around one roller in the final drying chamber, but care is taken so that if the sheet is bent, this is accomplished before the resin sets up hard. In this example the final drying was accomplished in two passes defined by a single roller and the roller was located at a point such that the sheet had not completely hardened at that place where the sheet was brought over the roller.

In the final drying the hot air for drying was admitted at the bottom of the drier and had a temperature of 400-550 F. and was withdrawn from the top of the drier by means of a suction fan. It may be noted that if the incoming air is not too hot and too dry during the preliminary drying of the sheet, prior to treatment with acid, the paper tends to blister due to the fact that vapor forms too rapidly within the sheet. Therefore, during the preliminary drying section the temperature is maintained somewhat lower than during the final drying section. During the final drying section the temperature may be raised to 400-550 F.

The phosphoric acid solution may be used in strengths up to but not substantially exceeding strength because at higher concentrations the catalyst tends to produce a yellow color on the paper. Other acids may be used, such as sul- Iuric, hydrochloric, acetic or other organic acids, and there may also be used acid producing salts, such as zinc chloride, ammonium chloride or alum.

Wad cutting 'The final, dry, brittle, hardened syrup-impregnated sheet was passed through a single action Waterbury Farrel press which was fitted with a plurality 01 dies spaced across the sheet for punching the wads. The press was also fitted with a feed mechanism so that as the dried impregnated paper was fed thereto the press punched out disks of the required size as the paper was fed.

As many apparently widely different embodiments of thisinvention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein.

What we claim is:

1. The continuous process of preparing brittle disintegratable top shot wads for shot shell cartridges which comprises immersing a fiexible absorbent cellulosic fibrous paperboard having a thickness of approximately 0.03 to 0.06 inch in an aqueous urea-formaldehyde syrup containing about 1.80 to 2.00 pounds of resin solids per gallon of syrup and having a pH of from about 6.2 to 8.2 for a period of about 4 to 5 minutes to substantially completely penetrate the fibers of the paperboard, heating said impregnated paperboard to a temperature of from about 300 to 400 F. so as to reduce the water content nearly to dryness, saturating said paperboard with an aqueous solution of an acidic catalyst, immediately further heating said paperboard at a temperature of from about 400 to 500 F. to finally dry said paperboard and condense said urea-formaldehyde thereby rendering said paperboard brittle and disintegratable, said impregnated paperboard being maintained in a uniformly planar, level condition during said final drying and condensation, and thereafter punching discs from the dry hardened fiat paperboard.

2. The process as set forth in claim 1 characterized in that said aqueous solution of an acidic catalyst comprises an aqueous solution of not substantially more than 10% by weight of a compound selected from the group consisting of phosphoric, sulfuric, hydrochloric and acetic acid.

and zinc chloride, ammonium chloride and alum.

HAROLD 0. RUSSELL. WILLIAM N. KING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,987,694 Mains Jan. 15, 1935 2,123,152 Rivat July 5, 1938 2,309,089 Bauer et al Jan. 26, 1943 2,325,302 Britt July 27, 1943 2,345,541 Scholze Mar. 28, 1944 2,376,200 Smidth May 16, 1945 FOREIGN PATENTS Number Country Date 108,354 Australia Sept. 7, 1939 

1. THE CONTINUOUS PROCESS OF PREPARING BRITTLE DISTINTEGRATABLE TOP SHOT WADS FOR SHOT SHELL CARTRIDGES WHICH COMPRISES IMMERSING A FLEXIBLE ABSORBENT CELLULOSIC FIBROUS PAPERBOARD HAVING A THICKNESS OF APPROXIMATELY 0.03 TO 0.06 INCH IN AN AQUEOUS UREA-FORMALDEHYDE SYRUP CONTAINING ABOUT 1.80 TO 2.00 POUNDS OF RESIN SOLIDS PER GALLON OF SYRUP AND HAVING A PH OF FROM ABOUT 6.2 TO 8.2 FOR A PERIOD OF ABOUT 4 TO 5 MINUTES TO SUBSTANTIALLY COMPLETELY PENETRATE THE FIBERS OF THE PAPERBOARD, HEATING SAID IMPREGNATED PAPERBOARD TO A TEMPERATURE OF FROM ABOUT 300 TO 400* F. SO AS TO REDUCE THE WATER CONTENT NEARLY TO DRYNESS, SATURATING SAID PAPERBOARD WITH AN AQUEOUS SOLUTION OF AN ACIDIC CATALYST, IMMEDIATELY FURTHER HEATING SAID PAPERBOARD AT A TEMPERATURE OF FROM ABOUT 400 TO 500* F. TO FINALLY DRY SAID PAPERBOARD AND CONDENSE SAID UREA-FORMALDEHYDE THEREBY RENDERING SAID PAPERBOARD BRITTLE AND DISINTEGRATBLE, SAID IMPREGNATED PAPERBOARD BEING MAINTAINED IN A UNIFORMLY PLANAR LEVEL CONDITION DURING SAID FINAL DRYING AND CONDENSATION, AND THEREAFTER PUNCHING DISCS FROM THE DRY HARDENED FLAT PAPERBOARD. 